The present invention relates to a rear-view optical system for protective helmets, in particular for helmets for use by cyclists, motorcyclists, car drivers and the like, both for pleasure and in sport and competition, and more particularly for helmets equipped with a visor.
No reliable and practical rear-view systems currently exist for helmets for use by motorcyclists or the like. U.S. Pat. No. 3,804,495 describes a rear-view system based on a set of reflecting mirrors. This system is cumbersome, in that it is fitted externally on the helmet and, more particularly, above a fixed visor projecting from the helmet. A rear-view system of this type, apart from being impractical, is not even compatible with today""s regulations on safety which prohibit the presence of projecting articles on a protective helmet.
IT-B-1 155 186 discloses a rear-view system incorporated in the thickness of the helmet. This dorsal viewing system entirely comprises reflective members such as prisms and mirrors. The system is cumbersome and incapable of providing a sufficiently broad view. Furthermore, the type of optics used are such as to require extensive space and therefore unacceptably weaken the structure of the helmet.
WO-A-97/10731 discloses a further rear-view system which envisages a channel cut out within the helmet. A series of mirrors disposed along the channel serves to guide the beam from the dorsal entry to the frontal exit. This system possesses, in addition to the disadvantages already mentioned with reference to the device described in IT-B-1 155 186, the disadvantage that the reflective surfaces are subject to soiling and cannot be accessed for effective cleaning, for which reason the system rapidly loses the ability to ensure an acceptable view.
Therefore, because of the inadequacy of the available solutions, use is currently made of rear-view mirrors fitted to the handlebars of vehicles (specifically bicycles and motorcycles). These mirrors are expensive, liable to break in the event of an accident, hazardous in that they project from the handlebar, and absolutely non-functional in that rearward vision is in any case difficult, especially for persons wearing a full helmet.
The subject of the present invention is a new rear-view system for protective helmets for use by motorcyclists, car drivers or the like, which does not exhibit the disadvantages of the traditional systems.
More specifically, an object of the present invention is to provide an optical system and a protective helmet which are compatible with the safety standards relating to protective helmets.
A further object of the present invention is to provide a helmet having a rear-view optical system which allows an easy and safe view of the scene behind and which at the same time does not interfere with the view of the scene in front and does not reduce the safety features of the helmet.
Yet another object of the present invention is to provide a helmet which makes it possible to avoid the need for using rear-view mirrors on vehicles, which are frequently costly, non-functional and inconvenient if not dangerous in that they are fitted on the handlebars of vehicles.
These and further objects and advantages, which will be clear to those skilled in the art from reading the text that follows, are achieved with a protective helmet comprising within its thickness at least one optical path, having a dorsal entry and a frontal exit, for conveying to the eye of the user an image of the scene behind said user""s back, characterized in that:
an objective lens is disposed at the point of said dorsal entry aperture;
an eyepiece is disposed at the point of said frontal exit;
a reflecting optical member is provided in front of said eyepiece and is positioned so as to reflect the image coming from said eyepiece toward the eye of the wearer of the helmet;
and at least one refractive member, and preferably two refractive members, are disposed along said optical path, between said objective and said eyepiece.
The use of the entry and exit optics makes it possible to produce a particularly narrow path which can therefore be disposed within the thickness of the helmet without affecting its features of shape and safety. Furthermore, the use of at least two refractive members make it possible to cause the beam to follow a curved optical path, which can thus follow the curvature of the helmet, remaining within the traditional outline of the latter. In particular, the use of the two refractive members makes it possible to produce an optical path which can extend at the height of the portion of the helmet which is located in the zone of the user""s ear. By this arrangement, it is possible to obtain deflections of the incoming beam through an angle equal to or greater than 25xc2x0 and preferably greater than 30xc2x0 before it reaches the reflective member. Depending on the angle of reflection achieved with the reflecting member located in front of the eyepiece, similar advantages can be obtained also with only one refractive member.
Either a portion or the whole of the optical path may be provided within a member applied to the main shell of the helmet. The path remains in any case internal to the whole thickness of the same helmet.
According to a possible embodiment of the invention, the two refractive members are symmetrical. They may take the form of two simple optical prisms. However, in order to obtain a high deflection of the optical beam, it is advantageous to arrange for each refractive member to comprise a pair of optical wedges having different refractive indexes. The two refractive members may be mutually different but are preferably symmetrical, that is to say each comprise a pair of optical wedges that are identical but mounted symmetrically.
The refractive members may possess an entry surface and an exit surface for the beam conveyed along said path which form an angle of between 25xc2x0 and 30xc2x0, and preferably approximately equal to 27xc2x0.
The two optical wedges may have refractive indexes of, for example, in excess of 1.65. Preferably, the first wedge possesses a refractive index in excess of 1.65 and the second of said optical wedges possesses a refractive index in excess of 1.75.
The eyepiece may advantageously comprise a lens which is adjustable for focusing, so as to permit simple adaptation to the visual capability of the person wearing the helmet. Furthermore, provision may advantageously be made for the reflective optical member to be mounted in a sleeve substantially coaxial with the eyepiece and capable of adjustment about the axis of the eyepiece to direct the beam correctly toward the eye of the user. In this manner, the helmet is made adaptable to the anatomical configuration of the person wearing it.
Preferably, there are two optical paths, normally but not necessarily symmetrical, in order to permit binocular rearward vision.
Further advantageous features and embodiments of the helmet according to the invention are indicated in the attached dependent claims.